Commit Graph

1797 Commits

Author SHA1 Message Date
Asias He 76aaa5101f block: Drop dead function blk_abort_queue()
This function was only used by btrfs code in btrfs_abort_devices()
(seems in a wrong way).

It was removed in commit d07eb91170,
So, Let's remove the dead code to avoid any confusion.

Changes in v2: update commit log, btrfs_abort_devices() was removed
already.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-kernel@vger.kernel.org
Cc: Chris Mason <chris.mason@oracle.com>
Cc: linux-btrfs@vger.kernel.org
Cc: David Sterba <dave@jikos.cz>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-15 08:46:23 +02:00
Asias He 5e5cfac0c6 block: Mitigate lock unbalance caused by lock switching
Commit 777eb1bf15 disconnects externally
supplied queue_lock before blk_drain_queue(). Switching the lock would
introduce lock unbalance because theads which have taken the external
lock might unlock the internal lock in the during the queue drain. This
patch mitigate this by disconnecting the lock after the queue draining
since queue draining makes a lot of request_queue users go away.

However, please note, this patch only makes the problem less likely to
happen. Anyone who still holds a ref might try to issue a new request on
a dead queue after the blk_cleanup_queue() finishes draining, the lock
unbalance might still happen in this case.

 =====================================
 [ BUG: bad unlock balance detected! ]
 3.4.0+ #288 Not tainted
 -------------------------------------
 fio/17706 is trying to release lock (&(&q->__queue_lock)->rlock) at:
 [<ffffffff81329372>] blk_queue_bio+0x2a2/0x380
 but there are no more locks to release!

 other info that might help us debug this:
 1 lock held by fio/17706:
  #0:  (&(&vblk->lock)->rlock){......}, at: [<ffffffff81327f1a>]
 get_request_wait+0x19a/0x250

 stack backtrace:
 Pid: 17706, comm: fio Not tainted 3.4.0+ #288
 Call Trace:
  [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380
  [<ffffffff810dea49>] print_unlock_inbalance_bug+0xf9/0x100
  [<ffffffff810dfe4f>] lock_release_non_nested+0x1df/0x330
  [<ffffffff811dae24>] ? dio_bio_end_aio+0x34/0xc0
  [<ffffffff811d6935>] ? bio_check_pages_dirty+0x85/0xe0
  [<ffffffff811daea1>] ? dio_bio_end_aio+0xb1/0xc0
  [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380
  [<ffffffff81329372>] ? blk_queue_bio+0x2a2/0x380
  [<ffffffff810e0079>] lock_release+0xd9/0x250
  [<ffffffff81a74553>] _raw_spin_unlock_irq+0x23/0x40
  [<ffffffff81329372>] blk_queue_bio+0x2a2/0x380
  [<ffffffff81328faa>] generic_make_request+0xca/0x100
  [<ffffffff81329056>] submit_bio+0x76/0xf0
  [<ffffffff8115470c>] ? set_page_dirty_lock+0x3c/0x60
  [<ffffffff811d69e1>] ? bio_set_pages_dirty+0x51/0x70
  [<ffffffff811dd1a8>] do_blockdev_direct_IO+0xbf8/0xee0
  [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80
  [<ffffffff811dd4e5>] __blockdev_direct_IO+0x55/0x60
  [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80
  [<ffffffff811d92e7>] blkdev_direct_IO+0x57/0x60
  [<ffffffff811d8620>] ? blkdev_get_block+0x80/0x80
  [<ffffffff8114c6ae>] generic_file_aio_read+0x70e/0x760
  [<ffffffff810df7c5>] ? __lock_acquire+0x215/0x5a0
  [<ffffffff811e9924>] ? aio_run_iocb+0x54/0x1a0
  [<ffffffff8114bfa0>] ? grab_cache_page_nowait+0xc0/0xc0
  [<ffffffff811e82cc>] aio_rw_vect_retry+0x7c/0x1e0
  [<ffffffff811e8250>] ? aio_fsync+0x30/0x30
  [<ffffffff811e9936>] aio_run_iocb+0x66/0x1a0
  [<ffffffff811ea9b0>] do_io_submit+0x6f0/0xb80
  [<ffffffff8134de2e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
  [<ffffffff811eae50>] sys_io_submit+0x10/0x20
  [<ffffffff81a7c9e9>] system_call_fastpath+0x16/0x1b

Changes since v2: Update commit log to explain how the code is still
                  broken even if we delay the lock switching after the drain.
Changes since v1: Update commit log as Tejun suggested.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-15 08:46:22 +02:00
Asias He 458f27a982 block: Avoid missed wakeup in request waitqueue
After hot-unplug a stressed disk, I found that rl->wait[] is not empty
while rl->count[] is empty and there are theads still sleeping on
get_request after the queue cleanup. With simple debug code, I found
there are exactly nr_sleep - nr_wakeup of theads in D state. So there
are missed wakeup.

  $ dmesg | grep nr_sleep
  [   52.917115] ---> nr_sleep=1046, nr_wakeup=873, delta=173
  $ vmstat 1
  1 173  0 712640  24292  96172 0 0  0  0  419  757  0  0  0 100  0

To quote Tejun:

  Ah, okay, freed_request() wakes up single waiter with the assumption
  that after the wakeup there will at least be one successful allocation
  which in turn will continue the wakeup chain until the wait list is
  empty - ie. waiter wakeup is dependent on successful request
  allocation happening after each wakeup.  With queue marked dead, any
  woken up waiter fails the allocation path, so the wakeup chaining is
  lost and we're left with hung waiters. What we need is wake_up_all()
  after drain completion.

This patch fixes the missed wakeup by waking up all the theads which
are sleeping on wait queue after queue drain.

Changes in v2: Drop waitqueue_active() optimization

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Asias He <asias@redhat.com>

Fixed a bug by me, where stacked devices would oops on calling
blk_drain_queue() since ->rq.wait[] do not get initialized unless
it's a full queue setup.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-15 08:45:25 +02:00
Tejun Heo 27e1f9d1cc blkcg: drop local variable @q from blkg_destroy()
blkg_destroy() caches @blkg->q in local variable @q.  While there are
two places which needs @blkg->q, only lockdep_assert_held() used the
local variable leading to unused local variable warning if lockdep is
configured out.  Drop the local variable and just use @blkg->q
directly.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Rakesh Iyer <rni@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-06 08:35:31 +02:00
Tejun Heo 9b2ea86bc9 blkcg: fix blkg_alloc() failure path
When policy data allocation fails in the middle, blkg_alloc() invokes
blkg_free() to destroy the half constructed blkg.  This ends up
calling pd_exit_fn() on policy datas which didn't go through
pd_init_fn().  Fix it by making blkg_alloc() call pd_init_fn()
immediately after each policy data allocation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-04 10:03:21 +02:00
Tejun Heo ffea73fc72 block: blkcg_policy_cfq shouldn't be used if !CONFIG_CFQ_GROUP_IOSCHED
cfq may be built w/ or w/o blkcg support depending on
CONFIG_CFQ_CGROUP_IOSCHED.  If blkcg support is disabled, most of
related code is ifdef'd out but some part is left dangling -
blkcg_policy_cfq is left zero-filled and blkcg_policy_[un]register()
calls are made on it.

Feeding zero filled policy to blkcg_policy_register() is incorrect and
triggers the following WARN_ON() if CONFIG_BLK_CGROUP &&
!CONFIG_CFQ_GROUP_IOSCHED.

 ------------[ cut here ]------------
 WARNING: at block/blk-cgroup.c:867
 Modules linked in:
 Modules linked in:
 CPU: 3 Not tainted 3.4.0-09547-gfb21aff #1
 Process swapper/0 (pid: 1, task: 000000003ff80000, ksp: 000000003ff7f8b8)
 Krnl PSW : 0704100180000000 00000000003d76ca (blkcg_policy_register+0xca/0xe0)
	    R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:0 CC:1 PM:0 EA:3
 Krnl GPRS: 0000000000000000 00000000014b85ec 00000000014b85b0 0000000000000000
	    000000000096fb60 0000000000000000 00000000009a8e78 0000000000000048
	    000000000099c070 0000000000b6f000 0000000000000000 000000000099c0b8
	    00000000014b85b0 0000000000667580 000000003ff7fd98 000000003ff7fd70
 Krnl Code: 00000000003d76be: a7280001           lhi     %r2,1
	    00000000003d76c2: a7f4ffdf           brc     15,3d7680
	   #00000000003d76c6: a7f40001           brc     15,3d76c8
	   >00000000003d76ca: a7c8ffea           lhi     %r12,-22
	    00000000003d76ce: a7f4ffce           brc     15,3d766a
	    00000000003d76d2: a7f40001           brc     15,3d76d4
	    00000000003d76d6: a7c80000           lhi     %r12,0
	    00000000003d76da: a7f4ffc2           brc     15,3d765e
 Call Trace:
 ([<0000000000b6f000>] initcall_debug+0x0/0x4)
  [<0000000000989e8a>] cfq_init+0x62/0xd4
  [<00000000001000ba>] do_one_initcall+0x3a/0x170
  [<000000000096fb60>] kernel_init+0x214/0x2bc
  [<0000000000623202>] kernel_thread_starter+0x6/0xc
  [<00000000006231fc>] kernel_thread_starter+0x0/0xc
 no locks held by swapper/0/1.
 Last Breaking-Event-Address:
  [<00000000003d76c6>] blkcg_policy_register+0xc6/0xe0
 ---[ end trace b8ef4903fcbf9dd3 ]---

This patch fixes the problem by ensuring all blkcg support code is
inside CONFIG_CFQ_GROUP_IOSCHED.

* blkcg_policy_cfq declaration and blkg_to_cfqg() definition are moved
  inside the first CONFIG_CFQ_GROUP_IOSCHED block.  __maybe_unused is
  dropped from blkcg_policy_cfq decl.

* blkcg_deactivate_poilcy() invocation is moved inside ifdef.  This
  also makes the activation logic match cfq_init_queue().

* All blkcg_policy_[un]register() invocations are moved inside ifdef.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
LKML-Reference: <20120601112954.GC3535@osiris.boeblingen.de.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-04 10:02:29 +02:00
Tejun Heo fd7949564c block: fix return value on cfq_init() failure
cfq_init() would return zero after kmem cache creation failure.  Fix
so that it returns -ENOMEM.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-06-04 10:01:38 +02:00
Eric Dumazet 3c9c708c9f block: avoid infinite loop in get_task_io_context()
Calling get_task_io_context() on a exiting task which isn't %current can
loop forever. This triggers at boot time on my dev machine.

BUG: soft lockup - CPU#3 stuck for 22s ! [mountall.1603]

Fix this by making create_task_io_context() returns -EBUSY in this case
to break the loop.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-05-31 13:39:05 +02:00
Linus Torvalds 0d167518e0 Merge branch 'for-3.5/core' of git://git.kernel.dk/linux-block
Merge block/IO core bits from Jens Axboe:
 "This is a bit bigger on the core side than usual, but that is purely
  because we decided to hold off on parts of Tejun's submission on 3.4
  to give it a bit more time to simmer.  As a consequence, it's seen a
  long cycle in for-next.

  It contains:

   - Bug fix from Dan, wrong locking type.
   - Relax splice gifting restriction from Eric.
   - A ton of updates from Tejun, primarily for blkcg.  This improves
     the code a lot, making the API nicer and cleaner, and also includes
     fixes for how we handle and tie policies and re-activate on
     switches.  The changes also include generic bug fixes.
   - A simple fix from Vivek, along with a fix for doing proper delayed
     allocation of the blkcg stats."

Fix up annoying conflict just due to different merge resolution in
Documentation/feature-removal-schedule.txt

* 'for-3.5/core' of git://git.kernel.dk/linux-block: (92 commits)
  blkcg: tg_stats_alloc_lock is an irq lock
  vmsplice: relax alignement requirements for SPLICE_F_GIFT
  blkcg: use radix tree to index blkgs from blkcg
  blkcg: fix blkcg->css ref leak in __blkg_lookup_create()
  block: fix elvpriv allocation failure handling
  block: collapse blk_alloc_request() into get_request()
  blkcg: collapse blkcg_policy_ops into blkcg_policy
  blkcg: embed struct blkg_policy_data in policy specific data
  blkcg: mass rename of blkcg API
  blkcg: style cleanups for blk-cgroup.h
  blkcg: remove blkio_group->path[]
  blkcg: blkg_rwstat_read() was missing inline
  blkcg: shoot down blkgs if all policies are deactivated
  blkcg: drop stuff unused after per-queue policy activation update
  blkcg: implement per-queue policy activation
  blkcg: add request_queue->root_blkg
  blkcg: make request_queue bypassing on allocation
  blkcg: make sure blkg_lookup() returns %NULL if @q is bypassing
  blkcg: make blkg_conf_prep() take @pol and return with queue lock held
  blkcg: remove static policy ID enums
  ...
2012-05-30 08:52:42 -07:00
Tejun Heo ff26eaadf4 blkcg: tg_stats_alloc_lock is an irq lock
tg_stats_alloc_lock nests inside queue lock and should always be held
with irq disabled.  throtl_pd_{init|exit}() were using non-irqsafe
spinlock ops which triggered inverse lock ordering via irq warning via
RCU freeing of blkg invoking throtl_pd_exit() w/o disabling IRQ.

Update both functions to use irq safe operations.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
LKML-Reference: <1335339396.16988.80.camel@lappy>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-05-23 12:16:21 +02:00
Linus Torvalds 88d6ae8dc3 Merge branch 'for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
 "cgroup file type addition / removal is updated so that file types are
  added and removed instead of individual files so that dynamic file
  type addition / removal can be implemented by cgroup and used by
  controllers.  blkio controller changes which will come through block
  tree are dependent on this.  Other changes include res_counter cleanup
  and disallowing kthread / PF_THREAD_BOUND threads to be attached to
  non-root cgroups.

  There's a reported bug with the file type addition / removal handling
  which can lead to oops on cgroup umount.  The issue is being looked
  into.  It shouldn't cause problems for most setups and isn't a
  security concern."

Fix up trivial conflict in Documentation/feature-removal-schedule.txt

* 'for-3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
  res_counter: Account max_usage when calling res_counter_charge_nofail()
  res_counter: Merge res_counter_charge and res_counter_charge_nofail
  cgroups: disallow attaching kthreadd or PF_THREAD_BOUND threads
  cgroup: remove cgroup_subsys->populate()
  cgroup: get rid of populate for memcg
  cgroup: pass struct mem_cgroup instead of struct cgroup to socket memcg
  cgroup: make css->refcnt clearing on cgroup removal optional
  cgroup: use negative bias on css->refcnt to block css_tryget()
  cgroup: implement cgroup_rm_cftypes()
  cgroup: introduce struct cfent
  cgroup: relocate __d_cgrp() and __d_cft()
  cgroup: remove cgroup_add_file[s]()
  cgroup: convert memcg controller to the new cftype interface
  memcg: always create memsw files if CONFIG_CGROUP_MEM_RES_CTLR_SWAP
  cgroup: convert all non-memcg controllers to the new cftype interface
  cgroup: relocate cftype and cgroup_subsys definitions in controllers
  cgroup: merge cft_release_agent cftype array into the base files array
  cgroup: implement cgroup_add_cftypes() and friends
  cgroup: build list of all cgroups under a given cgroupfs_root
  cgroup: move cgroup_clear_directory() call out of cgroup_populate_dir()
  ...
2012-05-22 17:40:19 -07:00
Linus Torvalds e60b9a0346 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Pull s390 updates from Martin Schwidefsky:
 "Just a random collection of bug-fixes and cleanups, nothing new in
  this merge request."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (46 commits)
  s390/ap: Fix wrong or missing comments
  s390/ap: move receive callback to message struct
  s390/dasd: re-prioritize partition detection message
  s390/qeth: reshuffle initialization
  s390/qeth: cleanup drv attr usage
  s390/claw: cleanup drv attr usage
  s390/lcs: cleanup drv attr usage
  s390/ctc: cleanup drv attr usage
  s390/ccwgroup: remove ccwgroup_create_from_string
  s390/qeth: stop using struct ccwgroup driver for discipline callbacks
  s390/qeth: switch to ccwgroup_create_dev
  s390/claw: switch to ccwgroup_create_dev
  s390/lcs: switch to ccwgroup_create_dev
  s390/ctcm: switch to ccwgroup_create_dev
  s390/ccwgroup: exploit ccwdev_by_dev_id
  s390/ccwgroup: introduce ccwgroup_create_dev
  s390: fix race on TIF_MCCK_PENDING
  s390/barrier: make use of fast-bcr facility
  s390/barrier: cleanup barrier functions
  s390/claw: remove "eieio" calls
  ...
2012-05-21 12:41:17 -07:00
Stefan Haberland 505e5ecfd3 s390/dasd: re-prioritize partition detection message
To avoid confusion while formatting a DASD device change the level of
the "Expected VOL1 label not found" message from warning to info.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2012-05-16 14:42:51 +02:00
Tejun Heo 05c69d298c block: fix buffer overflow when printing partition UUIDs
6d1d8050b4 "block, partition: add partition_meta_info to hd_struct"
added part_unpack_uuid() which assumes that the passed in buffer has
enough space for sprintfing "%pU" - 37 characters including '\0'.

Unfortunately, b5af921ec0 "init: add support for root devices
specified by partition UUID" supplied 33 bytes buffer to the function
leading to the following panic with stackprotector enabled.

  Kernel panic - not syncing: stack-protector: Kernel stack corrupted in: ffffffff81b14c7e

  [<ffffffff815e226b>] panic+0xba/0x1c6
  [<ffffffff81b14c7e>] ? printk_all_partitions+0x259/0x26xb
  [<ffffffff810566bb>] __stack_chk_fail+0x1b/0x20
  [<ffffffff81b15c7e>] printk_all_paritions+0x259/0x26xb
  [<ffffffff81aedfe0>] mount_block_root+0x1bc/0x27f
  [<ffffffff81aee0fa>] mount_root+0x57/0x5b
  [<ffffffff81aee23b>] prepare_namespace+0x13d/0x176
  [<ffffffff8107eec0>] ? release_tgcred.isra.4+0x330/0x30
  [<ffffffff81aedd60>] kernel_init+0x155/0x15a
  [<ffffffff81087b97>] ? schedule_tail+0x27/0xb0
  [<ffffffff815f4d24>] kernel_thread_helper+0x5/0x10
  [<ffffffff81aedc0b>] ? start_kernel+0x3c5/0x3c5
  [<ffffffff815f4d20>] ? gs_change+0x13/0x13

Increase the buffer size, remove the dangerous part_unpack_uuid() and
use snprintf() directly from printk_all_partitions().

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Szymon Gruszczynski <sz.gruszczynski@googlemail.com>
Cc: Will Drewry <wad@chromium.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-05-15 08:22:04 +02:00
Jens Axboe 0b7877d4ee Linux 3.4-rc5
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Merge tag 'v3.4-rc5' into for-3.5/core

The core branch is behind driver commits that we want to build
on for 3.5, hence I'm pulling in a later -rc.

Linux 3.4-rc5

Conflicts:
	Documentation/feature-removal-schedule.txt

Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-05-01 14:29:55 +02:00
Tejun Heo a637120e49 blkcg: use radix tree to index blkgs from blkcg
blkg lookup is currently performed by traversing linked list anchored
at blkcg->blkg_list.  This is very unscalable and with blk-throttle
enabled and enough request queues on the system, this can get very
ugly quickly (blk-throttle performs look up on every bio submission).

This patch makes blkcg use radix tree to index blkgs combined with
simple last-looked-up hint.  This is mostly identical to how icqs are
indexed from ioc.

Note that because __blkg_lookup() may be invoked without holding queue
lock, hint is only updated from __blkg_lookup_create().  Due to cfq's
cfqq caching, this makes hint updates overly lazy.  This will be
improved with scheduled blkcg aware request allocation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:40 +02:00
Tejun Heo 496fb7806d blkcg: fix blkcg->css ref leak in __blkg_lookup_create()
__blkg_lookup_create() leaked blkcg->css ref if blkg allocation
failed.  Fix it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:40 +02:00
Tejun Heo aaf7c68068 block: fix elvpriv allocation failure handling
Request allocation is mempool backed to guarantee forward progress
under memory pressure; unfortunately, this property got broken while
adding elvpriv data.  Failures during elvpriv allocation, including
ioc and icq creation failures, currently make get_request() fail as
whole.  There's no forward progress guarantee for these allocations -
they may fail indefinitely under memory pressure stalling IO and
deadlocking the system.

This patch updates get_request() such that elvpriv allocation failure
doesn't make the whole function fail.  If elvpriv allocation fails,
the allocation is degraded into !ELVPRIV.  This will force the request
to ELEVATOR_INSERT_BACK disturbing scheduling but elvpriv alloc
failures should be rare (nothing is per-request) and anything is
better than deadlocking.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:40 +02:00
Tejun Heo 29e2b09ab5 block: collapse blk_alloc_request() into get_request()
Allocation failure handling in get_request() is about to be updated.
To ease the update, collapse blk_alloc_request() into get_request().

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:40 +02:00
Tejun Heo f9fcc2d391 blkcg: collapse blkcg_policy_ops into blkcg_policy
There's no reason to keep blkcg_policy_ops separate.  Collapse it into
blkcg_policy.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:17 +02:00
Tejun Heo f95a04afa8 blkcg: embed struct blkg_policy_data in policy specific data
Currently blkg_policy_data carries policy specific data as char flex
array instead of being embedded in policy specific data.  This was
forced by oddities around blkg allocation which are all gone now.

This patch makes blkg_policy_data embedded in policy specific data -
throtl_grp and cfq_group so that it's more conventional and consistent
with how io_cq is handled.

* blkcg_policy->pdata_size is renamed to ->pd_size.

* Functions which used to take void *pdata now takes struct
  blkg_policy_data *pd.

* blkg_to_pdata/pdata_to_blkg() updated to blkg_to_pd/pd_to_blkg().

* Dummy struct blkg_policy_data definition added.  Dummy
  pdata_to_blkg() definition was unused and inconsistent with the
  non-dummy version - correct dummy pd_to_blkg() added.

* throtl and cfq updated accordingly.

* As dummy blkg_to_pd/pd_to_blkg() are provided,
  blkg_to_cfqg/cfqg_to_blkg() don't need to be ifdef'd.  Moved outside
  ifdef block.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:17 +02:00
Tejun Heo 3c798398e3 blkcg: mass rename of blkcg API
During the recent blkcg cleanup, most of blkcg API has changed to such
extent that mass renaming wouldn't cause any noticeable pain.  Take
the chance and cleanup the naming.

* Rename blkio_cgroup to blkcg.

* Drop blkio / blkiocg prefixes and consistently use blkcg.

* Rename blkio_group to blkcg_gq, which is consistent with io_cq but
  keep the blkg prefix / variable name.

* Rename policy method type and field names to signify they're dealing
  with policy data.

* Rename blkio_policy_type to blkcg_policy.

This patch doesn't cause any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:17 +02:00
Tejun Heo 36558c8a30 blkcg: style cleanups for blk-cgroup.h
* Update indentation on struct field declarations.

* Uniformly don't use "extern" on function declarations.

* Merge the two #ifdef CONFIG_BLK_CGROUP blocks.

All changes in this patch are cosmetic.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:16 +02:00
Tejun Heo 54e7ed12ba blkcg: remove blkio_group->path[]
blkio_group->path[] stores the path of the associated cgroup and is
used only for debug messages.  Just format the path from blkg->cgroup
when printing debug messages.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:16 +02:00
Tejun Heo c94bed8999 blkcg: blkg_rwstat_read() was missing inline
blkg_rwstat_read() in blk-cgroup.h was missing inline modifier causing
compile warning depending on configuration.  Add it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:16 +02:00
Tejun Heo 6d18b008da blkcg: shoot down blkgs if all policies are deactivated
There's no reason to keep blkgs around if no policy is activated for
the queue.  This patch moves queue locking out of blkg_destroy_all()
and call it from blkg_deactivate_policy() on deactivation of the last
policy on the queue.

This change was suggested by Vivek.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo 3c96cb32d3 blkcg: drop stuff unused after per-queue policy activation update
* All_q_list is unused.  Drop all_q_{mutex|list}.

* @for_root of blkg_lookup_create() is always %false when called from
  outside blk-cgroup.c proper.  Factor out __blkg_lookup_create() so
  that it doesn't check whether @q is bypassing and use the
  underscored version for the @for_root callsite.

* blkg_destroy_all() is used only from blkcg proper and @destroy_root
  is always %true.  Make it static and drop @destroy_root.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo a2b1693bac blkcg: implement per-queue policy activation
All blkcg policies were assumed to be enabled on all request_queues.
Due to various implementation obstacles, during the recent blkcg core
updates, this was temporarily implemented as shooting down all !root
blkgs on elevator switch and policy [de]registration combined with
half-broken in-place root blkg updates.  In addition to being buggy
and racy, this meant losing all blkcg configurations across those
events.

Now that blkcg is cleaned up enough, this patch replaces the temporary
implementation with proper per-queue policy activation.  Each blkcg
policy should call the new blkcg_[de]activate_policy() to enable and
disable the policy on a specific queue.  blkcg_activate_policy()
allocates and installs policy data for the policy for all existing
blkgs.  blkcg_deactivate_policy() does the reverse.  If a policy is
not enabled for a given queue, blkg printing / config functions skip
the respective blkg for the queue.

blkcg_activate_policy() also takes care of root blkg creation, and
cfq_init_queue() and blk_throtl_init() are updated accordingly.

This replaces blkcg_bypass_{start|end}() and update_root_blkg_pd()
unnecessary.  Dropped.

v2: cfq_init_queue() was returning uninitialized @ret on root_group
    alloc failure if !CONFIG_CFQ_GROUP_IOSCHED.  Fixed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo 03d8e11142 blkcg: add request_queue->root_blkg
With per-queue policy activation, root blkg creation will be moved to
blkcg core.  Add q->root_blkg in preparation.  For blk-throtl, this
replaces throtl_data->root_tg; however, cfq needs to keep
cfqd->root_group for !CONFIG_CFQ_GROUP_IOSCHED.

This is to prepare for per-queue policy activation and doesn't cause
any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo b82d4b197c blkcg: make request_queue bypassing on allocation
With the previous change to guarantee bypass visiblity for RCU read
lock regions, entering bypass mode involves non-trivial overhead and
future changes are scheduled to make use of bypass mode during init
path.  Combined it may end up adding noticeable delay during boot.

This patch makes request_queue start its life in bypass mode, which is
ended on queue init completion at the end of
blk_init_allocated_queue(), and updates blk_queue_bypass_start() such
that draining and RCU synchronization are performed only when the
queue actually enters bypass mode.

This avoids unnecessarily switching in and out of bypass mode during
init avoiding the overhead and any nasty surprises which may step from
leaving bypass mode on half-initialized queues.

The boot time overhead was pointed out by Vivek.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo 80fd99792b blkcg: make sure blkg_lookup() returns %NULL if @q is bypassing
Currently, blkg_lookup() doesn't check @q bypass state.  This patch
updates blk_queue_bypass_start() to do synchronize_rcu() before
returning and updates blkg_lookup() to check blk_queue_bypass() and
return %NULL if bypassing.  This ensures blkg_lookup() returns %NULL
if @q is bypassing.

This is to guarantee that nobody is accessing policy data while @q is
bypassing, which is necessary to allow replacing blkio_cgroup->pd[] in
place on policy [de]activation.

v2: Added more comments explaining bypass guarantees as suggested by
    Vivek.

v3: Added more comments explaining why there's no synchronize_rcu() in
    blk_cleanup_queue() as suggested by Vivek.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo da8b066262 blkcg: make blkg_conf_prep() take @pol and return with queue lock held
Add @pol to blkg_conf_prep() and let it return with queue lock held
(to be released by blkg_conf_finish()).  Note that @pol isn't used
yet.

This is to prepare for per-queue policy activation and doesn't cause
any visible difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo 8bd435b30e blkcg: remove static policy ID enums
Remove BLKIO_POLICY_* enums and let blkio_policy_register() allocate
@pol->plid dynamically on registration.  The maximum number of blkcg
policies which can be registered at the same time is defined by
BLKCG_MAX_POLS constant added to include/linux/blkdev.h.

Note that blkio_policy_register() now may fail.  Policy init functions
updated accordingly and unnecessary ifdefs removed from cfq_init().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo ec399347d3 blkcg: use @pol instead of @plid in update_root_blkg_pd() and blkcg_print_blkgs()
The two functions were taking "enum blkio_policy_id plid".  Make them
take "const struct blkio_policy_type *pol" instead.

This is to prepare for per-queue policy activation and doesn't cause
any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo bc0d6501a8 blkcg: kill blkio_list and replace blkio_list_lock with a mutex
With blkio_policy[], blkio_list is redundant and hinders with
per-queue policy activation.  Remove it.  Also, replace
blkio_list_lock with a mutex blkcg_pol_mutex and let it protect the
whole [un]registration.

This is to prepare for per-queue policy activation and doesn't cause
any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Tejun Heo f48ec1d788 cfq: fix build breakage & warnings
* CFQ_WEIGHT_* defined inside CONFIG_BLK_CGROUP causes cfq-iosched.c
  compile failure when the config is disabled.  Move it outside the
  ifdef block.

* Dummy cfqg_stats_*() definitions were lacking inline modifiers
  causing unused functions warning if !CONFIG_CFQ_GROUP_IOSCHED.  Add
  them.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-20 10:06:06 +02:00
Linus Torvalds d8dd0b6d48 Merge branch 'for-3.4/core' of git://git.kernel.dk/linux-block
Pull block core bits from Jens Axboe:
 "It's a nice and quiet round this time, since most of the tricky stuff
  has been pushed to 3.5 to give it more time to mature.  After a few
  hectic block IO core changes for 3.3 and 3.2, I'm quite happy with a
  slow round.

  Really minor stuff in here, the only real functional change is making
  the auto-unplug threshold a per-queue entity.  The threshold is set so
  that it's low enough that we don't hold off IO for too long, but still
  big enough to get a nice benefit from the batched insert (and hence
  queue lock cost reduction).  For raid configurations, this currently
  breaks down."

* 'for-3.4/core' of git://git.kernel.dk/linux-block:
  block: make auto block plug flush threshold per-disk based
  Documentation: Add sysfs ABI change for cfq's target latency.
  block: Make cfq_target_latency tunable through sysfs.
  block: use lockdep_assert_held for queue locking
  block: blk_alloc_queue_node(): use caller's GFP flags instead of GFP_KERNEL
2012-04-13 18:07:19 -07:00
Shaohua Li 1b2e19f17e block: make auto block plug flush threshold per-disk based
We do auto block plug flush to reduce latency, the threshold is 16
requests. This works well if the task is accessing one or two drives.
The problem is if the task is accessing a raid 0 device and the raid
disk number is big, say 8 or 16, 16/8 = 2 or 16/16=1, we will have
heavy lock contention.

This patch makes the threshold per-disk based. The latency should be
still ok accessing one or two drives. The setup with application
accessing a lot of drives in the meantime uaually is big machine,
avoiding lock contention is more important, because any contention
will actually increase latency.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-06 11:37:47 -06:00
Tejun Heo 5bc4afb1ec blkcg: drop BLKCG_STAT_{PRIV|POL|OFF} macros
Now that all stat handling code lives in policy implementations,
there's no need to encode policy ID in cft->private.

* Export blkcg_prfill_[rw]stat() from blkcg, remove
  blkcg_print_[rw]stat(), and implement cfqg_print_[rw]stat() which
  use hard-code BLKIO_POLICY_PROP.

* Use cft->private for offset of the target field directly and drop
  BLKCG_STAT_{PRIV|POL|OFF}().

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:45 -07:00
Tejun Heo d366e7ec41 blkcg: pass around pd->pdata instead of pd itself in prfill functions
Now that all conf and stat fields are moved into policy specific
blkio_policy_data->pdata areas, there's no reason to use
blkio_policy_data itself in prfill functions.  Pass around @pd->pdata
instead of @pd.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:44 -07:00
Tejun Heo af133ceb26 blkcg: move blkio_group_conf->iops and ->bps to blk-throttle
blkio_cgroup_conf->iops and ->bps are owned by blk-throttle and has no
reason to be defined in blkcg core.  Drop them and let conf setting
functions directly manipulate throtl_grp->bps[] and ->iops[].

This makes blkio_group_conf empty.  Drop it.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:44 -07:00
Tejun Heo 3381cb8d2e blkcg: move blkio_group_conf->weight to cfq
blkio_group_conf->weight is owned by cfq and has no reason to be
defined in blkcg core.  Replace it with cfq_group->dev_weight and let
conf setting functions directly set it.  If dev_weight is zero, the
cfqg doesn't have device specific weight configured.

Also, rename BLKIO_WEIGHT_* constants to CFQ_WEIGHT_* and rename
blkio_cgroup->weight to blkio_cgroup->cfq_weight.  We eventually want
per-policy storage in blkio_cgroup but just mark the ownership of the
field for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:44 -07:00
Tejun Heo 8a3d26151f blkcg: move blkio_group_stats_cpu and friends to blk-throttle.c
blkio_group_stats_cpu is used only by blk-throtl and has no reason to
be defined in blkcg core.

* Move blkio_group_stats_cpu to blk-throttle.c and rename it to
  tg_stats_cpu.

* blkg_policy_data->stats_cpu is replaced with throtl_grp->stats_cpu.
  prfill functions updated accordingly.

* All related macros / functions are renamed so that they have tg_
  prefix and the unnecessary @pol arguments are dropped.

* Per-cpu stats allocation code is also moved from blk-cgroup.c to
  blk-throttle.c and gets simplified to only deal with
  BLKIO_POLICY_THROTL.  percpu stat free is performed by the exit
  method throtl_exit_blkio_group().

* throtl_reset_group_stats() implemented for
  blkio_reset_group_stats_fn method so that tg->stats_cpu can be
  reset.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:44 -07:00
Tejun Heo 155fead9b6 blkcg: move blkio_group_stats to cfq-iosched.c
blkio_group_stats contains only fields used by cfq and has no reason
to be defined in blkcg core.

* Move blkio_group_stats to cfq-iosched.c and rename it to cfqg_stats.

* blkg_policy_data->stats is replaced with cfq_group->stats.
  blkg_prfill_[rw]stat() are updated to use offset against pd->pdata
  instead.

* All related macros / functions are renamed so that they have cfqg_
  prefix and the unnecessary @pol arguments are dropped.

* All stat functions now take cfq_group * instead of blkio_group *.

* lockdep assertion on queue lock dropped.  Elevator runs under queue
  lock by default.  There isn't much to be gained by adding lockdep
  assertions at stat function level.

* cfqg_stats_reset() implemented for blkio_reset_group_stats_fn method
  so that cfqg->stats can be reset.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:44 -07:00
Tejun Heo 9ade5ea4ce blkcg: add blkio_policy_ops operations for exit and stat reset
Add blkio_policy_ops->blkio_exit_group_fn() and
->blkio_reset_group_stats_fn().  These will be used to further
modularize blkcg policy implementation.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:44 -07:00
Tejun Heo 41b38b6d54 blkcg: cfq doesn't need per-cpu dispatch stats
blkio_group_stats_cpu is used to count dispatch stats using per-cpu
counters.  This is used by both blk-throtl and cfq-iosched but the
sharing is rather silly.

* cfq-iosched doesn't need per-cpu dispatch stats.  cfq always updates
  those stats while holding queue_lock.

* blk-throtl needs per-cpu dispatch stats but only service_bytes and
  serviced.  It doesn't make use of sectors.

This patch makes cfq add and use global stats for service_bytes,
serviced and sectors, removes per-cpu sectors counter and moves
per-cpu stat printing code to blk-throttle.c.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:44 -07:00
Tejun Heo 629ed0b102 blkcg: move statistics update code to policies
As with conf/stats file handling code, there's no reason for stat
update code to live in blkcg core with policies calling into update
them.  The current organization is both inflexible and complex.

This patch moves stat update code to specific policies.  All
blkiocg_update_*_stats() functions which deal with BLKIO_POLICY_PROP
stats are collapsed into their cfq_blkiocg_update_*_stats()
counterparts.  blkiocg_update_dispatch_stats() is used by both
policies and duplicated as throtl_update_dispatch_stats() and
cfq_blkiocg_update_dispatch_stats().  This will be cleaned up later.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:44 -07:00
Tejun Heo 2ce4d50f9c cfq: collapse cfq.h into cfq-iosched.c
block/cfq.h contains some functions which interact with blkcg;
however, this is only part of it and cfq-iosched.c already has quite
some #ifdef CONFIG_CFQ_GROUP_IOSCHED.  With conf/stat handling being
moved to specific policies, having these relay functions isolated in
cfq.h doesn't make much sense.  Collapse cfq.h into cfq-iosched.c for
now.  Let's split blkcg support properly later if necessary.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:43 -07:00
Tejun Heo 60c2bc2d5a blkcg: move conf/stat file handling code to policies
blkcg conf/stat handling is convoluted in that details which belong to
specific policy implementations are all out in blkcg core and then
policies hook into core layer to access and manipulate confs and
stats.  This sadly achieves both inflexibility (confs/stats can't be
modified without messing with blkcg core) and complexity (all the
call-ins and call-backs).

The previous patches restructured conf and stat handling code such
that they can be separated out.  This patch relocates the file
handling part.  All conf/stat file handling code which belongs to
BLKIO_POLICY_PROP is moved to cfq-iosched.c and all
BKLIO_POLICY_THROTL code to blk-throtl.c.

The move is verbatim except for blkio_update_group_{weight|bps|iops}()
callbacks which relays conf changes to policies.  The configuration
settings are handled in policies themselves so the relaying isn't
necessary.  Conf setting functions are modified to directly call
per-policy update functions and the relaying mechanism is dropped.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:43 -07:00
Tejun Heo 44ea53de46 blkcg: implement blkio_policy_type->cftypes
Add blkiop->cftypes which is added and removed together with the
policy.  This will be used to move conf/stat handling to the policies.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:43 -07:00
Tejun Heo 829fdb5000 blkcg: export conf/stat helpers to prepare for reorganization
conf/stat handling is about to be moved to policy implementation from
blkcg core.  Export conf/stat helpers from blkcg core so that
blk-throttle and cfq-iosched can use them.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:43 -07:00
Tejun Heo 726fa6945e blkcg: simplify blkg_conf_prep()
blkg_conf_prep() implements "MAJ:MIN VAL" parsing manually, which is
unnecessary.  Just use sscanf("%u:%u %llu").  This might not reject
some malformed input (extra input at the end) but we don't care.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:43 -07:00
Tejun Heo 3a8b31d396 blkcg: restructure blkio_group configruation setting
As part of userland interface restructuring, this patch updates
per-blkio_group configuration setting.  Instead of funneling
everything through a master function which has hard-coded cases for
each config file it may handle, the common part is factored into
blkg_conf_prep() and blkg_conf_finish() and different configuration
setters are implemented using the helpers.

While this doesn't result in immediate LOC reduction, this enables
further cleanups and more modular implementation.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:43 -07:00
Tejun Heo c4682aec9c blkcg: restructure configuration printing
Similarly to the previous stat restructuring, this patch restructures
conf printing code such that,

* Conf printing uses the same helpers as stat.

* Printing function doesn't require hardcoded switching on the config
  being printed.  Note that this isn't complete yet for throttle
  confs.  The next patch will convert setting for these confs and will
  complete the transition.

* Printing uses read_seq_string callback (other methods will be phased
  out).

Note that blkio_group_conf.iops[2] is changed to u64 so that they can
be manipulated with the same functions.  This is transitional and will
go away later.

After this patch, per-device configurations - weight, bps and iops -
use __blkg_prfill_u64() for printing which uses white space as
delimiter instead of tab.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:43 -07:00
Tejun Heo 627f29f481 blkcg: drop blkiocg_file_write_u64()
blkiocg_file_write_u64() has single switch case.  Drop
blkiocg_file_write_u64(), rename blkio_weight_write() to
blkcg_set_weight() and use it directly for .write_u64 callback.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:43 -07:00
Tejun Heo d3d32e69fa blkcg: restructure statistics printing
blkcg stats handling is a mess.  None of the stats has much to do with
blkcg core but they are all implemented in blkcg core.  Code sharing
is achieved by mixing common code with hard-coded cases for each stat
counter.

This patch restructures statistics printing such that

* Common logic exists as helper functions and specific print functions
  use the helpers to implement specific cases.

* Printing functions serving multiple counters don't require hardcoded
  switching on specific counters.

* Printing uses read_seq_string callback (other methods will be phased
  out).

This change enables further cleanups and relocating stats code to the
policy implementation it belongs to.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:42 -07:00
Tejun Heo edcb0722c6 blkcg: introduce blkg_stat and blkg_rwstat
blkcg uses u64_stats_sync to avoid reading wrong u64 statistic values
on 32bit archs and some stat counters have subtypes to distinguish
read/writes and sync/async IOs.  The stat code paths are confusing and
involve a lot of going back and forth between blkcg core and specific
policy implementations, and synchronization and subtype handling are
open coded in blkcg core.

This patch introduces struct blkg_stat and blkg_rwstat which, with
accompanying operations, encapsulate stat updating and accessing with
proper synchronization.

blkg_stat is simple u64 counter with 64bit read-access protection.
blkg_rwstat is the one with rw and [a]sync subcounters and takes @rw
flags to distinguish IO subtypes (%REQ_WRITE and %REQ_SYNC) and
replaces stat_sub_type indexed arrays.

All counters in blkio_group_stats and blkio_group_stats_cpu are
replaced with either blkg_stat or blkg_rwstat along with all users.

This does add one u64_stats_sync per counter and increase stats_sync
operations but they're empty/noops on 64bit archs and blkcg doesn't
have too many counters, especially with DEBUG_BLK_CGROUP off.

While the currently resulting code isn't necessarily simpler at the
moment, this will enable further clean up of blkcg stats code.

- BLKIO_STAT_{READ|WRITE|SYNC|ASYNC|TOTAL} renamed to
  BLKG_RWSTAT_{READ|WRITE|SYNC|ASYNC|TOTAL}.

- blkg_stat_add() replaces blkio_add_stat() and
  blkio_check_and_dec_stat().  Note that BUG_ON() on underflow in the
  latter function no longer exists.  It's *way* better to have
  underflowed stat counters than oopsing.

- blkio_group_stats->dequeue is now a proper u64 stat counter instead
  of ulong.

- reset_stats() updated to clear each stat counters individually and
  BLKG_STATS_DEBUG_CLEAR_{START|SIZE} are removed.

- Some functions reconstruct rw flags from direction and sync
  booleans.  This will be removed by future patches.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:42 -07:00
Tejun Heo 2aa4a1523b blkcg: BLKIO_STAT_CPU_SECTORS doesn't have subcounters
BLKIO_STAT_CPU_SECTORS doesn't need read/write/sync/async subcounters
and is counted by blkio_group_stats_cpu->sectors; however, it still
holds a member in blkio_group_stats_cpu->stat_arr_cpu.

Rearrange stat_type_cpu and define BLKIO_STAT_CPU_ARR_NR and use it
for stat_arr_cpu[] size so that only SERVICE_BYTES and SERVICED have
subcounters.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:42 -07:00
Tejun Heo aaec55a002 blkcg: remove unused @pol and @plid parameters
@pol to blkg_to_pdata() and @plid to blkg_lookup_create() are no
longer necessary.  Drop them.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 14:38:42 -07:00
Tao Ma 5bf14c0727 block: Make cfq_target_latency tunable through sysfs.
In cfq, when we calculate a time slice for a process(or a cfqq to
be precise), we have to consider the cfq_target_latency so that all the
sync request have an estimated latency(300ms) and it is controlled by
cfq_target_latency. But in some hadoop test, we have found that if
there are many processes doing sequential read(24 for example), the
throughput is bad because every process can only work for about 25ms
and the cfqq is switched. That leads to a higher disk seek. We can
achive the good throughput by setting low_latency=0, but then some
read's latency is too much for the application.

So this patch makes cfq_target_latency tunable through sysfs so that
we can tune it and find some magic number which is not bad for both
the throughput and the read latency.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-04-01 14:33:39 -07:00
Tejun Heo 959d851caa Merge branch 'for-3.5' of ../cgroup into block/for-3.5/core-merged
cgroup/for-3.5 contains the following changes which blk-cgroup needs
to proceed with the on-going cleanup.

* Dynamic addition and removal of cftypes to make config/stat file
  handling modular for policies.

* cgroup removal update to not wait for css references to drain to fix
  blkcg removal hang caused by cfq caching cfqgs.

Pull in cgroup/for-3.5 into block/for-3.5/core.  This causes the
following conflicts in block/blk-cgroup.c.

* 761b3ef50e "cgroup: remove cgroup_subsys argument from callbacks"
  conflicts with blkiocg_pre_destroy() addition and blkiocg_attach()
  removal.  Resolved by removing @subsys from all subsys methods.

* 676f7c8f84 "cgroup: relocate cftype and cgroup_subsys definitions in
  controllers" conflicts with ->pre_destroy() and ->attach() updates
  and removal of modular config.  Resolved by dropping forward
  declarations of the methods and applying updates to the relocated
  blkio_subsys.

* 4baf6e3325 "cgroup: convert all non-memcg controllers to the new
  cftype interface" builds upon the previous item.  Resolved by adding
  ->base_cftypes to the relocated blkio_subsys.

Signed-off-by: Tejun Heo <tj@kernel.org>
2012-04-01 12:55:00 -07:00
Tejun Heo 4baf6e3325 cgroup: convert all non-memcg controllers to the new cftype interface
Convert debug, freezer, cpuset, cpu_cgroup, cpuacct, net_prio, blkio,
net_cls and device controllers to use the new cftype based interface.
Termination entry is added to cftype arrays and populate callbacks are
replaced with cgroup_subsys->base_cftypes initializations.

This is functionally identical transformation.  There shouldn't be any
visible behavior change.

memcg is rather special and will be converted separately.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <paul@paulmenage.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vivek Goyal <vgoyal@redhat.com>
2012-04-01 12:09:55 -07:00
Tejun Heo 676f7c8f84 cgroup: relocate cftype and cgroup_subsys definitions in controllers
blk-cgroup, netprio_cgroup, cls_cgroup and tcp_memcontrol
unnecessarily define cftype array and cgroup_subsys structures at the
top of the file, which is unconventional and necessiates forward
declaration of methods.

This patch relocates those below the definitions of the methods and
removes the forward declarations.  Note that forward declaration of
tcp_files[] is added in tcp_memcontrol.c for tcp_init_cgroup().  This
will be removed soon by another patch.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
2012-04-01 12:09:55 -07:00
Andi Kleen 8bcb6c7d48 block: use lockdep_assert_held for queue locking
Instead of an ugly open coded variant.

Cc: axboe@kernel.dk
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-30 12:33:28 +02:00
Dan Carpenter a5567932fc blkcg: change a spin_lock() to spin_lock_irq()
Smatch complains that we re-enable IRQs twice.  It looks like we forgot
to disable them here on the spin_trylock() failure path.  This was added
in 9f13ef678e "blkcg: use double locking instead of RCU for blkg
synchronization".

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>`
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-29 20:57:08 +02:00
Tejun Heo eb7d8c07f9 cfq: fix cfqg ref handling when BLK_CGROUP && !CFQ_GROUP_IOSCHED
When BLK_CGROUP is enabled but CFQ_GROUP_IOSCHED is, cfq ends up
calling blkg_get/put() on dummy cfqg leading to the following crash.

  BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0
  IP: [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430
  PGD 0
  Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
  CPU 0
  Modules linked in:

  Pid: 1, comm: swapper/0 Not tainted 3.3.0-rc6-work+ #125 Bochs Bochs
  RIP: 0010:[<ffffffff813d44d8>]  [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430
  RSP: 0018:ffff88001f9dfd80  EFLAGS: 00010046
  RAX: ffff88001aefbbf0 RBX: ffff88001aeedbf0 RCX: 0000000000000100
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff820ffd40
  RBP: ffff88001f9dfdd0 R08: 0000000000000000 R09: 0000000000000001
  R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
  R13: 0000000000000009 R14: ffff88001aefbc30 R15: 0000000000000003
  FS:  0000000000000000(0000) GS:ffff88001fc00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
  CR2: 00000000000000b0 CR3: 000000000206f000 CR4: 00000000000006f0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
  Process swapper/0 (pid: 1, threadinfo ffff88001f9de000, task ffff88001f9dc040)
  Stack:
   ffff88001aeedbf0 ffff88001aefbdb0 ffff88001aef1548 ffff88001aefbbf0
   ffff88001f9dfdd0 ffff88001aef1548 ffffffff820d6320 ffffffff8165ce30
   ffffffff82c555e0 ffff88001aeebbf0 ffff88001f9dfe00 ffffffff813b0507
  Call Trace:
   [<ffffffff813b0507>] elevator_init+0xd7/0x140
   [<ffffffff813b83d5>] blk_init_allocated_queue+0x125/0x150
   [<ffffffff813b94d3>] blk_init_queue_node+0x43/0x80
   [<ffffffff813b9523>] blk_init_queue+0x13/0x20
   [<ffffffff821aec00>] floppy_init+0x82/0xec7
   [<ffffffff810001d2>] do_one_initcall+0x42/0x170
   [<ffffffff821835fc>] kernel_init+0xcb/0x14f
   [<ffffffff81b40b24>] kernel_thread_helper+0x4/0x10
  Code: 00 e8 1d 9e 76 00 48 8b 43 48 48 85 c0 48 89 83 28 03 00 00 74 07 4c 8b a0 10 ff ff ff 8b 15 b0 2e d0 00 85 d2 0f 85 49 01 00 00 <41> 8b 84 24 b0 00 00 00 85 c0 0f 8e 8c 01 00 00 83 e8 01 85 c0
  RIP  [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430

Because cfq's blkcg support has a on/off switch, CFQ_GROUP_IOSCHED,
separate from BLK_CGROUP, blkg access through cfqg needs to be
conditioned on it.

* Make blkg_to_cfqg() and cfqg_to_blkg() conditioned on
  CFQ_GROUP_IOSCHED.  If disabled, they always return %NULL.

* Introduce cfqg_get() and cfqg_put() conditioned on
  CFQ_GROUP_IOSCHED.  If disabled, they are noops.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-23 14:02:53 +01:00
Dan Carpenter 00380a404f block: blk_alloc_queue_node(): use caller's GFP flags instead of GFP_KERNEL
We should use the GFP flags that the caller specified instead of picking
our own.  All the callers specify GFP_KERNEL so this doesn't make a
difference to how the kernel runs, it's just a cleanup.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-23 09:58:54 +01:00
Linus Torvalds 0d9cabdcce Merge branch 'for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup changes from Tejun Heo:
 "Out of the 8 commits, one fixes a long-standing locking issue around
  tasklist walking and others are cleanups."

* 'for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Walk task list under tasklist_lock in cgroup_enable_task_cg_list
  cgroup: Remove wrong comment on cgroup_enable_task_cg_list()
  cgroup: remove cgroup_subsys argument from callbacks
  cgroup: remove extra calls to find_existing_css_set
  cgroup: replace tasklist_lock with rcu_read_lock
  cgroup: simplify double-check locking in cgroup_attach_proc
  cgroup: move struct cgroup_pidlist out from the header file
  cgroup: remove cgroup_attach_task_current_cg()
2012-03-20 18:11:21 -07:00
Linus Torvalds 2ba68940c8 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler changes for v3.4 from Ingo Molnar

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  printk: Make it compile with !CONFIG_PRINTK
  sched/x86: Fix overflow in cyc2ns_offset
  sched: Fix nohz load accounting -- again!
  sched: Update yield() docs
  printk/sched: Introduce special printk_sched() for those awkward moments
  sched/nohz: Correctly initialize 'next_balance' in 'nohz' idle balancer
  sched: Cleanup cpu_active madness
  sched: Fix load-balance wreckage
  sched: Clean up parameter passing of proc_sched_autogroup_set_nice()
  sched: Ditch per cgroup task lists for load-balancing
  sched: Rename load-balancing fields
  sched: Move load-balancing arguments into helper struct
  sched/rt: Do not submit new work when PI-blocked
  sched/rt: Prevent idle task boosting
  sched/wait: Add __wake_up_all_locked() API
  sched/rt: Document scheduler related skip-resched-check sites
  sched/rt: Use schedule_preempt_disabled()
  sched/rt: Add schedule_preempt_disabled()
  sched/rt: Do not throttle when PI boosting
  sched/rt: Keep period timer ticking when rt throttling is active
  ...
2012-03-20 10:31:44 -07:00
Tejun Heo 2b566fa55b block: remove ioc_*_changed()
After the previous patch to cfq, there's no ioc_get_changed() user
left.  This patch yanks out ioc_{ioprio|cgroup|get}_changed() and all
related stuff.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:47:48 +01:00
Tejun Heo 598971bfbd cfq: don't use icq_get_changed()
cfq caches the associated cfqq's for a given cic.  The cache needs to
be flushed if the cic's ioprio or blkcg has changed.  It is currently
done by requiring the changing action to set the respective
ICQ_*_CHANGED bit in the icq and testing it from cfq_set_request(),
which involves iterating through all the affected icqs.

All cfq wants to know is whether ioprio and/or blkcg have changed
since the last flush and can be easily achieved by just remembering
the current ioprio and blkcg ID in cic.

This patch adds cic->{ioprio|blkcg_id}, updates all ioprio users to
use the remembered value instead, and updates cfq_set_request() path
such that, instead of using icq_get_changed(), the current values are
compared against the remembered ones and trigger appropriate flush
action if not.  Condition tests are moved inside both _changed
functions which are now named check_ioprio_changed() and
check_blkcg_changed().

ioprio.h::task_ioprio*() can't be used anymore and replaced with
open-coded IOPRIO_CLASS_NONE case in cfq_async_queue_prio().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:47:47 +01:00
Tejun Heo abede6da27 cfq: pass around cfq_io_cq instead of io_context
Now that io_cq is managed by block core and guaranteed to exist for
any in-flight request, it is easier and carries more information to
pass around cfq_io_cq than io_context.

This patch updates cfq_init_prio_data(), cfq_find_alloc_queue() and
cfq_get_queue() to take @cic instead of @ioc.  This change removes a
duplicate cfq_cic_lookup() from cfq_find_alloc_queue().

This change enables the use of cic-cached ioprio in the next patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:47:47 +01:00
Tejun Heo 9a9e8a26da blkcg: add blkcg->id
Add 64bit unique id to blkcg.  This will be used by policies which
want blkcg identity test to tell whether the associated blkcg has
changed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:47:47 +01:00
Tejun Heo edf1b879e3 blkcg: remove blkio_group->stats_lock
With recent plug merge updates, all non-percpu stat updates happen
under queue_lock making stats_lock unnecessary to synchronize stat
updates.  The only synchronization necessary is stat reading, which
can be done using u64_stats_sync instead.

This patch removes blkio_group->stats_lock and adds
blkio_group_stats->syncp for reader synchronization.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:45:37 +01:00
Tejun Heo c4c76a0538 blkcg: restructure blkio_get_stat()
Restructure blkio_get_stat() to prepare for removal of stats_lock.

* Define BLKIO_STAT_ARR_NR explicitly to denote which stats have
  subtypes instead of using BLKIO_STAT_QUEUED.

* Separate out stat acquisition and printing.  After this, there are
  only two users of blkio_fill_stat().  Just open code it.

* The code was mixing MAX_KEY_LEN and MAX_KEY_LEN - 1.  There's no
  need to subtract one.  Use MAX_KEY_LEN consistently.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:45:37 +01:00
Tejun Heo 997a026c80 blkcg: simplify stat reset
blkiocg_reset_stats() implements stat reset for blkio.reset_stats
cgroupfs file.  This feature is very unconventional and something
which shouldn't have been merged.  It's only useful when there's only
one user or tool looking at the stats.  As soon as multiple users
and/or tools are involved, it becomes useless as resetting disrupts
other usages.  There are very good reasons why all other stats expect
readers to read values at the start and end of a period and subtract
to determine delta over the period.

The implementation is rather complex - some fields shouldn't be
cleared and it saves some fields, resets whole and restores for some
reason.  Reset of percpu stats is also racy.  The comment points to
64bit store atomicity for the reason but even without that stores for
zero can simply race with other CPUs doing RMW and get clobbered.

Simplify reset by

* Clear selectively instead of resetting and restoring.

* Grouping debug stat fields to be reset and using memset() over them.

* Not caring about stats_lock.

* Using memset() to reset percpu stats.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:45:37 +01:00
Tejun Heo 5fe224d2d5 blkcg: don't use percpu for merged stats
With recent plug merge updates, merged stats are no longer called for
plug merges and now only updated while holding queue_lock.  As
stats_lock is scheduled to be removed, there's no reason to use percpu
for merged stats.  Don't use percpu for merged stats.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:45:37 +01:00
Vivek Goyal 1cd9e039fc blkcg: alloc per cpu stats from worker thread in a delayed manner
Current per cpu stat allocation assumes GFP_KERNEL allocation flag. But in
IO path there are times when we want GFP_NOIO semantics. As there is no
way to pass the allocation flags to alloc_percpu(), this patch delays the
allocation of stats using a worker thread.

v2-> tejun suggested following changes. Changed the patch accordingly.
	- move alloc_node location in structure
	- reduce the size of names of some of the fields
	- Reduce the scope of locking of alloc_list_lock
	- Simplified stat_alloc_fn() by allocating stats for all
	  policies in one go and then assigning these to a group.

v3 -> Andrew suggested to put some comments in the code. Also raised
      concerns about trying to allocate infinitely in case of allocation
      failure. I have changed the logic to sleep for 10ms before retrying.
      That should take care of non-preemptible UP kernels.

v4 -> Tejun had more suggestions.
	- drop list_for_each_entry_all()
	- instead of msleep() use queue_delayed_work()
	- Some cleanups realted to more compact coding.

v5-> tejun suggested more cleanups leading to more compact code.

tj: - Relocated pcpu_stats into blkio_stat_alloc_fn().
    - Minor comment update.
    - This also fixes suspicious RCU usage warning caused by invoking
      cgroup_path() from blkg_alloc() without holding RCU read lock.
      Now that blkg_alloc() doesn't require sleepable context, RCU
      read lock from blkg_lookup_create() is maintained throughout
      blkg_alloc().

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-20 12:45:37 +01:00
Linus Torvalds f1cbd03f5e Merge branch 'for-linus' of git://git.kernel.dk/linux-block
Pull block fixes from Jens Axboe:
 "Been sitting on this for a while, but lets get this out the door.
  This fixes various important bugs for 3.3 final, along with a few more
  trivial ones.  Please pull!"

* 'for-linus' of git://git.kernel.dk/linux-block:
  block: fix ioc leak in put_io_context
  block, sx8: fix pointer math issue getting fw version
  Block: use a freezable workqueue for disk-event polling
  drivers/block/DAC960: fix -Wuninitialized warning
  drivers/block/DAC960: fix DAC960_V2_IOCTL_Opcode_T -Wenum-compare warning
  block: fix __blkdev_get and add_disk race condition
  block: Fix setting bio flags in drivers (sd_dif/floppy)
  block: Fix NULL pointer dereference in sd_revalidate_disk
  block: exit_io_context() should call elevator_exit_icq_fn()
  block: simplify ioc_release_fn()
  block: replace icq->changed with icq->flags
2012-03-14 17:16:45 -07:00
Xiaotian Feng ff8c1474cc block: fix ioc leak in put_io_context
When put_io_context is called, if ioc->icq_list is empty and refcount
is 1, kernel will not free the ioc.

This is caught by following kmemleak:

unreferenced object 0xffff880036349fe0 (size 216):
  comm "sh", pid 2137, jiffies 4294931140 (age 290579.412s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    01 00 01 00 ad 4e ad de ff ff ff ff 00 00 00 00  .....N..........
  backtrace:
    [<ffffffff8169f926>] kmemleak_alloc+0x26/0x50
    [<ffffffff81195a9c>] kmem_cache_alloc_node+0x1cc/0x2a0
    [<ffffffff81356b67>] create_io_context_slowpath+0x27/0x130
    [<ffffffff81356d2b>] get_task_io_context+0xbb/0xf0
    [<ffffffff81055f0e>] copy_process+0x188e/0x18b0
    [<ffffffff8105609b>] do_fork+0x11b/0x420
    [<ffffffff810247f8>] sys_clone+0x28/0x30
    [<ffffffff816d3373>] stub_clone+0x13/0x20
    [<ffffffffffffffff>] 0xffffffffffffffff

ioc should be freed if ioc->icq_list is empty.
Signed-off-by: Xiaotian Feng <dannyfeng@tencent.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-14 15:34:48 +01:00
Tejun Heo 671058fb2a block: make blk-throttle preserve the issuing task on delayed bios
Make blk-throttle call bio_associate_current() on bios being delayed
such that they get issued to block layer with the original io_context.
This allows stacking blk-throttle and cfq-iosched propio policies.
bios will always be issued with the correct ioc and blkcg whether it
gets delayed by blk-throttle or not.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:24 +01:00
Tejun Heo 4f85cb96d9 block: make block cgroup policies follow bio task association
Implement bio_blkio_cgroup() which returns the blkcg associated with
the bio if exists or %current's blkcg, and use it in blk-throttle and
cfq-iosched propio.  This makes both cgroup policies honor task
association for the bio instead of always assuming %current.

As nobody is using bio_set_task() yet, this doesn't introduce any
behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:24 +01:00
Tejun Heo 852c788f83 block: implement bio_associate_current()
IO scheduling and cgroup are tied to the issuing task via io_context
and cgroup of %current.  Unfortunately, there are cases where IOs need
to be routed via a different task which makes scheduling and cgroup
limit enforcement applied completely incorrectly.

For example, all bios delayed by blk-throttle end up being issued by a
delayed work item and get assigned the io_context of the worker task
which happens to serve the work item and dumped to the default block
cgroup.  This is double confusing as bios which aren't delayed end up
in the correct cgroup and makes using blk-throttle and cfq propio
together impossible.

Any code which punts IO issuing to another task is affected which is
getting more and more common (e.g. btrfs).  As both io_context and
cgroup are firmly tied to task including userland visible APIs to
manipulate them, it makes a lot of sense to match up tasks to bios.

This patch implements bio_associate_current() which associates the
specified bio with %current.  The bio will record the associated ioc
and blkcg at that point and block layer will use the recorded ones
regardless of which task actually ends up issuing the bio.  bio
release puts the associated ioc and blkcg.

It grabs and remembers ioc and blkcg instead of the task itself
because task may already be dead by the time the bio is issued making
ioc and blkcg inaccessible and those are all block layer cares about.

elevator_set_req_fn() is updated such that the bio elvdata is being
allocated for is available to the elevator.

This doesn't update block cgroup policies yet.  Further patches will
implement the support.

-v2: #ifdef CONFIG_BLK_CGROUP added around bio->bi_ioc dereference in
     rq_ioc() to fix build breakage.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Kent Overstreet <koverstreet@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:24 +01:00
Tejun Heo f6e8d01bee block: add io_context->active_ref
Currently ioc->nr_tasks is used to decide two things - whether an ioc
is done issuing IOs and whether it's shared by multiple tasks.  This
patch separate out the first into ioc->active_ref, which is acquired
and released using {get|put}_io_context_active() respectively.

This will be used to associate bio's with a given task.  This patch
doesn't introduce any visible behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:24 +01:00
Tejun Heo 24acfc34fb block: interface update for ioc/icq creation functions
Make the following interface updates to prepare for future ioc related
changes.

* create_io_context() returning ioc only works for %current because it
  doesn't increment ref on the ioc.  Drop @task parameter from it and
  always assume %current.

* Make create_io_context_slowpath() return 0 or -errno and rename it
  to create_task_io_context().

* Make ioc_create_icq() take @ioc as parameter instead of assuming
  that of %current.  The caller, get_request(), is updated to create
  ioc explicitly and then pass it into ioc_create_icq().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:24 +01:00
Tejun Heo b679281a64 block: restructure get_request()
get_request() is structured a bit unusually in that failure path is
inlined in the usual flow with goto labels atop and inside it.
Relocate the error path to the end of the function.

This is to prepare for icq handling changes in get_request() and
doesn't introduce any behavior change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:24 +01:00
Tejun Heo c875f4d025 blkcg: drop unnecessary RCU locking
Now that blkg additions / removals are always done under both q and
blkcg locks, the only places RCU locking is necessary are
blkg_lookup[_create]() for lookup w/o blkcg lock.  This patch drops
unncessary RCU locking replacing it with plain blkcg locking as
necessary.

* blkiocg_pre_destroy() already perform proper locking and don't need
  RCU.  Dropped.

* blkio_read_blkg_stats() now uses blkcg->lock instead of RCU read
  lock.  This isn't a hot path.

* Now unnecessary synchronize_rcu() from queue exit paths removed.
  This makes q->nr_blkgs unnecessary.  Dropped.

* RCU annotation on blkg->q removed.

-v2: Vivek pointed out that blkg_lookup_create() still needs to be
     called under rcu_read_lock().  Updated.

-v3: After the update, stats_lock locking in blkio_read_blkg_stats()
     shouldn't be using _irq variant as it otherwise ends up enabling
     irq while blkcg->lock is locked.  Fixed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:24 +01:00
Tejun Heo 9f13ef678e blkcg: use double locking instead of RCU for blkg synchronization
blkgs are chained from both blkcgs and request_queues and thus
subjected to two locks - blkcg->lock and q->queue_lock.  As both blkcg
and q can go away anytime, locking during removal is tricky.  It's
currently solved by wrapping removal inside RCU, which makes the
synchronization complex.  There are three locks to worry about - the
outer RCU, q lock and blkcg lock, and it leads to nasty subtle
complications like conditional synchronize_rcu() on queue exit paths.

For all other paths, blkcg lock is naturally nested inside q lock and
the only exception is blkcg removal path, which is a very cold path
and can be implemented as clumsy but conceptually-simple reverse
double lock dancing.

This patch updates blkg removal path such that blkgs are removed while
holding both q and blkcg locks, which is trivial for request queue
exit path - blkg_destroy_all().  The blkcg removal path,
blkiocg_pre_destroy(), implements reverse double lock dancing
essentially identical to ioc_release_fn().

This simplifies blkg locking - no half-dead blkgs to worry about.  Now
unnecessary RCU annotations will be removed by the next patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:24 +01:00
Tejun Heo e8989fae38 blkcg: unify blkg's for blkcg policies
Currently, blkg is per cgroup-queue-policy combination.  This is
unnatural and leads to various convolutions in partially used
duplicate fields in blkg, config / stat access, and general management
of blkgs.

This patch make blkg's per cgroup-queue and let them serve all
policies.  blkgs are now created and destroyed by blkcg core proper.
This will allow further consolidation of common management logic into
blkcg core and API with better defined semantics and layering.

As a transitional step to untangle blkg management, elvswitch and
policy [de]registration, all blkgs except the root blkg are being shot
down during elvswitch and bypass.  This patch adds blkg_root_update()
to update root blkg in place on policy change.  This is hacky and racy
but should be good enough as interim step until we get locking
simplified and switch over to proper in-place update for all blkgs.

-v2: Root blkgs need to be updated on elvswitch too and blkg_alloc()
     comment wasn't updated according to the function change.  Fixed.
     Both pointed out by Vivek.

-v3: v2 updated blkg_destroy_all() to invoke update_root_blkg_pd() for
     all policies.  This freed root pd during elvswitch before the
     last queue finished exiting and led to oops.  Directly invoke
     update_root_blkg_pd() only on BLKIO_POLICY_PROP from
     cfq_exit_queue().  This also is closer to what will be done with
     proper in-place blkg update.  Reported by Vivek.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo 03aa264ac1 blkcg: let blkcg core manage per-queue blkg list and counter
With the previous patch to move blkg list heads and counters to
request_queue and blkg, logic to manage them in both policies are
almost identical and can be moved to blkcg core.

This patch moves blkg link logic into blkg_lookup_create(), implements
common blkg unlink code in blkg_destroy(), and updates
blkg_destory_all() so that it's policy specific and can skip root
group.  The updated blkg_destroy_all() is now used to both clear queue
for bypassing and elv switching, and release all blkgs on q exit.

This patch introduces a race window where policy [de]registration may
race against queue blkg clearing.  This can only be a problem on cfq
unload and shouldn't be a real problem in practice (and we have many
other places where this race already exists).  Future patches will
remove these unlikely races.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo 4eef304998 blkcg: move per-queue blkg list heads and counters to queue and blkg
Currently, specific policy implementations are responsible for
maintaining list and number of blkgs.  This duplicates code
unnecessarily, and hinders factoring common code and providing blkcg
API with better defined semantics.

After this patch, request_queue hosts list heads and counters and blkg
has list nodes for both policies.  This patch only relocates the
necessary fields and the next patch will actually move management code
into blkcg core.

Note that request_queue->blkg_list[] and ->nr_blkgs[] are hardcoded to
have 2 elements.  This is to avoid include dependency and will be
removed by the next patch.

This patch doesn't introduce any behavior change.

-v2: Now unnecessary conditional on CONFIG_BLK_CGROUP_MODULE removed
     as pointed out by Vivek.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo c1768268f9 blkcg: don't use blkg->plid in stat related functions
blkg is scheduled to be unified for all policies and thus there won't
be one-to-one mapping from blkg to policy.  Update stat related
functions to take explicit @pol or @plid arguments and not use
blkg->plid.

This is painful for now but most of specific stat interface functions
will be replaced with a handful of generic helpers.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo 549d3aa872 blkcg: make blkg->pd an array and move configuration and stats into it
To prepare for unifying blkgs for different policies, make blkg->pd an
array with BLKIO_NR_POLICIES elements and move blkg->conf, ->stats,
and ->stats_cpu into blkg_policy_data.

This patch doesn't introduce any functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo 1adaf3dde3 blkcg: move refcnt to blkcg core
Currently, blkcg policy implementations manage blkg refcnt duplicating
mostly identical code in both policies.  This patch moves refcnt to
blkg and let blkcg core handle refcnt and freeing of blkgs.

* cfq blkgs now also get freed via RCU.

* cfq blkgs lose RB_EMPTY_ROOT() sanity check on blkg free.  If
  necessary, we can add blkio_exit_group_fn() to resurrect this.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo 0381411e4b blkcg: let blkcg core handle policy private data allocation
Currently, blkg's are embedded in private data blkcg policy private
data structure and thus allocated and freed by policies.  This leads
to duplicate codes in policies, hinders implementing common part in
blkcg core with strong semantics, and forces duplicate blkg's for the
same cgroup-q association.

This patch introduces struct blkg_policy_data which is a separate data
structure chained from blkg.  Policies specifies the amount of private
data it needs in its blkio_policy_type->pdata_size and blkcg core
takes care of allocating them along with blkg which can be accessed
using blkg_to_pdata().  blkg can be determined from pdata using
pdata_to_blkg().  blkio_alloc_group_fn() method is accordingly updated
to blkio_init_group_fn().

For consistency, tg_of_blkg() and cfqg_of_blkg() are replaced with
blkg_to_tg() and blkg_to_cfqg() respectively, and functions to map in
the reverse direction are added.

Except that policy specific data now lives in a separate data
structure from blkg, this patch doesn't introduce any functional
difference.

This will be used to unify blkg's for different policies.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo 923adde1be blkcg: clear all request_queues on blkcg policy [un]registrations
Keep track of all request_queues which have blkcg initialized and turn
on bypass and invoke blkcg_clear_queue() on all before making changes
to blkcg policies.

This is to prepare for moving blkg management into blkcg core.  Note
that this uses more brute force than necessary.  Finer grained shoot
down will be implemented later and given that policy [un]registration
almost never happens on running systems (blk-throtl can't be built as
a module and cfq usually is the builtin default iosched), this
shouldn't be a problem for the time being.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo 5efd611351 blkcg: add blkcg_{init|drain|exit}_queue()
Currently block core calls directly into blk-throttle for init, drain
and exit.  This patch adds blkcg_{init|drain|exit}_queue() which wraps
the blk-throttle functions.  This is to give more control and
visiblity to blkcg core layer for proper layering.  Further patches
will add logic common to blkcg policies to the functions.

While at it, collapse blk_throtl_release() into blk_throtl_exit().
There's no reason to keep them separate.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Tejun Heo 7ee9c56205 blkcg: let blkio_group point to blkio_cgroup directly
Currently, blkg points to the associated blkcg via its css_id.  This
unnecessarily complicates dereferencing blkcg.  Let blkg hold a
reference to the associated blkcg and point directly to it and disable
css_id on blkio_subsys.

This change requires splitting blkiocg_destroy() into
blkiocg_pre_destroy() and blkiocg_destroy() so that all blkg's can be
destroyed and all the blkcg references held by them dropped during
cgroup removal.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:23 +01:00
Vivek Goyal 92616b5b3a blkcg: skip blkg printing if q isn't associated with disk
blk-cgroup printing code currently assumes that there is a device/disk
associated with every queue in the system, but modules like floppy,
can instantiate request queues without registering disk which can lead
to oops.

Skip the queue/blkg which don't have dev/disk associated with them.

-tj: Factored out backing_dev_info check into blkg_dev_name().

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:22 +01:00
Tejun Heo 7a4dd281ec blkcg: kill the mind-bending blkg->dev
blkg->dev is dev_t recording the device number of the block device for
the associated request_queue.  It is used to identify the associated
block device when printing out configuration or stats.

This is redundant to begin with.  A blkg is an association between a
cgroup and a request_queue and it of course is possible to reach
request_queue from blkg and synchronization conventions are in place
for safe q dereferencing, so this shouldn't be necessary from the
beginning.  Furthermore, it's initialized by sscanf()ing the device
name of backing_dev_info.  The mind boggles.

Anyways, if blkg is visible under rcu lock, we *know* that the
associated request_queue hasn't gone away yet and its bdi is
registered and alive - blkg can't be created for request_queue which
hasn't been fully initialized and it can't go away before blkg is
removed.

Let stat and conf read functions get device name from
blkg->q->backing_dev_info.dev and pass it down to printing functions
and remove blkg->dev.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-06 21:27:22 +01:00